You do not need to be connected to T-Mobile's network or have a R-Mobile SIM in the TMB U firmware loaded Note 9, S9/S9 Plus, and Note 8 to still receive updates. These updates are pushed by Samsung through their Update App. The only exception are devices loaded with the AT&T firmware, because AT&T insists their devices try to stay locked down to deter customers from taking their devuces to other companies. The only devices that get updates mostly on time, are Google Nexus and Pixel devices.